The present invention relates to a composite member comprising a polyacetal resin and another polymeric material (specifically, an elastic material) directly adhering to each other, as well as to a production process thereof.
Polyacetal resins were launched into mass production by Du Pont (E.I.) de Nemours and Co. and Celanese Corp. in about the 1960s and have been used in a variety of fields since then, as they are very excellent in fatigue resistance and have satisfactory physical properties in balance such as friction/abrasion resistance, low-noise property, chemical resistance, creep resistance, and dimensional stability. On the other hand, such a polyacetal resin has poor affinity to other organic materials due to its specific chemical structure, as compared with other engineering plastics, and therefore is used alone. Additionally, there is no appropriate adhesive to combine the polyacetal resin with another material, as the polyacetal resin is resistant to adhesion. Specifically, there are strong demands to combine the polyacetal resin with an elastic material to make use of its satisfactory physical properties, but the demands cannot be significantly responded to due to the above technical reasons.
Accordingly, an object of the present invention is to provide a composite which includes a polyacetal resin and another polymeric material firmly adhering to each other, and a production process thereof.
Another object of the present invention is to provide a composite which includes a polyacetal resin and another polymeric material directly adhering to each other without the medium of an adhesive.
After intensive investigations to achieve the above objects, the present inventors found that heating of a polyacetal resin and a thermoplastic resin or elastomer having an acidic group permits an interface between the both materials to firmly bind and fix with each other. The present invention has been accomplished based on these findings.
Specifically, the present invention provides, in an aspect, a polyacetal composite which includes a polymer unit (A) composed of a polyacetal resin, and a polymer unit (B) composed of a thermoplastic resin or elastomer having an acidic group, and the polymer unit (A) and the polymer unit (B) directly adhere to each other. The acidic group includes, for example, a carboxyl group and a carboxylic anhydride group. The thermoplastic resin or elastomer having an acidic group includes, for example, a copolymer having, as a comonomer, at least one selected from among acrylic acid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride, and itaconic acid. The thermoplastic resin or elastomer having an acidic group includes, for example, an acid-modified polystyrene and an acid-modified NBR (acid-modified nitrile rubber).
In another aspect, the present invention provides a process for producing a polyacetal composite which includes the step of bringing a composition containing a polyacetal resin into contact with a composition containing a thermoplastic resin or elastomer having an acidic group (including the case where the thermoplastic resin or elastomer having an acidic group alone is contained) under heating to thereby yield a composite including a polymer unit (A) composed of the polyacetal resin, and a polymer unit (B) composed of the thermoplastic resin or elastomer having an acidic group, in which the polymer unit (A) and the polymer unit (B) directly adhere to each other.
In the present description, xe2x80x9crubberxe2x80x9d and xe2x80x9cthermoplastic elastomerxe2x80x9d are generically referred to as xe2x80x9celastomerxe2x80x9d. The term xe2x80x9ccomposition containing a polyacetal resinxe2x80x9d also includes the case where the composition contains a polyacetal resin alone. Likewise, the term xe2x80x9ccomposition containing a thermoplastic resin or elastomer having an acidic groupxe2x80x9d also includes the case where the composition contains the thermoplastic resin or elastomer having an acidic group alone.